Hi David,
Dave Hillman had it just right when he responded to ' [TN] Axial Part Age';
since I can not improve upon it and you, judging from your question, have
missed it will repeat it for you. Dave Hillman wrote:

>Hi Joe - if only predicting solderability was that easy! The industry
>"norms", if there is really such a unit of measure, is that a majority of
>component manufacturers will state that the component solderability is good
>for 12 months and many will extend that out for 24 months. After that
>everyone becomes silent. Three forcing functions become part of the
>equation: 1) what is the condition of the component finish?; 2) what is the
>storage environment?; 3) what flux will be used during the soldering
>process? A good, thick tin lead surface finish(e.g. 120 microinches) can
>last for several years but a thin tin lead surface finish could oxidize or
>have intermetallic exposure problems within months. A gold finish could
>last indefinitely but if it has too much porosity then the basis metal
>oxidizes very quickly. The storage environment you mention is very benign
>but lack of humidity and temperature controls will impact the surface
>finish. Last, the flux used in the soldering operation may be active enough
>to overcome any surface finish oxidation/intermetallic problems that may be
>present. The interaction of these three variables is why getting a
>black&white answer to storage life prediction for a component finish is so
>tough. Steam aging is NOT a simulation of storage life but only a condition
>method that can be used to understand how robust a surface finish is (that
>is a widely misunderstood concept). The Alternative Finishes task group is
>going to be looking into conditioning methods for surface finishes in the
>next year including reassessment of steam aging (maybe we should say steam
>conditioning) so hopefully some good information will become available for
>the industry to use.
>
>Dave Hillman
>Rockwell Collins
>[log in to unmask]

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 973-543-2747
E-mail: [log in to unmask]

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################